Stupid question--but why wouldn't the factory do this if it was easy hp? I assume you're driving all the accessories (alternator, steering pump, water pump, AC pump, etc.) slower. Doesn't sound like a good idea under some conditions. Never considered these so havn't looked into them.

Can't say what compromises the factory made. I am unsure if the S65 V8 has an electric water pump but the S85 V10 is belt driven. The car does dyno better (+28 RWHP) at the expense of a slight temp increase.

in the M5 / M6's the slight increase in temp doesn't seem to affect anything and universally people think the engine revs quicker.

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"Aerodynamics are for people who cannot build engines"......Enzo Ferrari